A gas inlet member is known from US 2009/0169744A1 and US 2006/0263522A1, in which a gas distribution volume is connected via tubes to the ceiling of a process chamber. Through the tubes, the process gas fed into the gas distribution volume can enter the process chamber located beneath the gas outlet plate. The process chamber ceiling here forms a gas outlet plate that forms a housing wall of a gas distribution volume.
DE 103 20 597 A1 describes a method and a device for depositing semiconductor layers using two process gases, the process gases being introduced into the process chamber through a gas inlet member.
DE 697 06 248 T2 describes a gas inlet member formed as a shower head, the gas lines of which are positioned on the vertices of triangles. Cooling chambers for cooling the gas inlet wall are present inside the gas inlet member.
U.S. Pat. No. 6,544,341 B1 describes a gas inlet member comprising a plurality of chambers arranged one above the other and having a multiplicity of gas outlet openings that are positioned on the vertices of equilateral triangles.
U.S. Pat. No. 7,976,631 B2 describes a gas inlet member that has cooled structures protruding out of the gas inlet housing wall toward the process chamber.
US 2006/0021574 A1 describes a gas inlet member, the process gas flowing through a porous gas outlet plate.
FIGS. 3 and 4 of DE 10 2006 018 515 A1 describe a gas inlet member which is part of a CVD reactor. The gas inlet member is shaped like a shower head and is arranged above a process chamber, the base of which is formed by a susceptor, on which substrates to be coated, in particular semiconductor substrates, can be placed. A gas outlet plate which is in contact with a gas inlet housing wall during the deposition process is present directly beneath the gas inlet member. The gas outlet plate can be displaced towards the susceptor for cleaning. Since the gas inlet housing wall of the gas inlet member is cooled and only the susceptor is heated, it is possible due to this measure to bring the gas outlet plate to a higher temperature so that by introducing an etching gas, for example HCl, parasitic deposits can be cleaned from the gas outlet plate.
In the case of CVD reactors having gas inlet members, the process chamber ceiling of which is formed by the gas inlet housing wall itself, parasitic growth occurs on the cooled gas inlet housing wall. This can result in undesirable particle formation within the process chamber. Moreover, the outlets of the gas feed lines can clog. This has the consequence that the gas inlet members have to be frequently mechanically cleaned. For cleaning the gas outlet side of the gas inlet member, the entire reactor housing has to be opened.
It is therefore an object of the invention to provide measures by which the cleaning cycles can be extended.
The gas outlet plate known from the above-mentioned prior art has openings for the process gas to pass through. Although the gas outlet plate is in contact with the cooled gas inlet wall, the gas outlet plate is still heated by heat conduction via the process gas through the process chamber, or via heat radiation from the susceptor. The outlet ends of the openings in the gas outlet plate can thus reach a temperature at which the process gas passing through the openings decomposes. The decomposition products can react with one another in the region of the outlet. This can also result in parasitic reactions in the gas phase, where undesirable adducts can form.
It is therefore a further object of the invention to provide measures by which undesirable pre-reactions can be reduced.
In the case of a CVD reactor in which the process chamber ceiling is cooled directly, the high heat dissipation requires that a high heat capacity must be provided in order to heat the susceptor to the desired process temperatures.
It is therefore a further object of the invention to increase the energy efficiency.
In a deposition process that uses hydrides, for example arsine or phosphine, which react in the process chamber together with organometallic compounds of main group III, moisture residues have negative effects on the layer growth.
It is therefore a further object of the invention to provide measures by which the moisture-inducing effects can be reduced.
At least one of these objects is achieved by the invention set forth in the claims.